Electrical amalgamator



April 16, 1940. G. MALMGREN 2,197,133

ELECTR I CAL AMALGAMATOR Filed June 28, 19s? 2 Sheets Sheet 1 IN V EN TOR GEORGE MAL MGRE/V. BY

A TTORN E Y5.

April 16, 1940.

ALKAL/ SALTS G. MALMGREN Filed June 28, 1937 PULP GAL VAN/C AC 7' ION,

AMALGAM PLA TES ELECTRICAL AMALGAMATOR 2 Sheets-Sheet 2 MERCURY AMALGAM PUL P TA IL ING'S RECOVERY OF ALKAL/ SAL TS kEco VERY of ALKAL/ SALTS PRECIOUS ME TALS AND MEI? C URV MERCURY INVENTOR,

GEORGE MAL MGREN. BY

A TTORNEYS.

Patented Apr; 16, 1940.

" uNir-EuSTAT S mes ' ELECTRICAL AMALGAMATOR George Malmgren, "Santa Cru Q'Califi. Application June 28, 1937, Serial No. 150,792

9 Claims. (01. 209 175) I g first screened wet totminus iii-mesh size, using a "dilute solution ofsodium or potassium sulphate, or amixture of both, for the wash water, and I My invention relates to --a-means and method for electrical amalgamation, and my invention is particularly desirable in the recovery of gold, sil- 'ver, and platinum values from sands, gravels or classified ores. I

Among the objects of my invention are? To provide an i amalgamato-r having'a continuous mercury flow; to providean"amalgamator utilizingthe, amalgamating" plates asone' pole of a galvanicbattery; to provide an amalgamator utilizing;electrical couples for cleaning-mercury during amalgamation; 'to provide a means and method of electrical amalgamation; to provide a means and method of continuously removing '1 values from an amalgamated plate; to "provide an amalgamator utilizingfiintermittent electrical energization'; and to providean efficient and con..

tinuous means and'method "of segregating values from a'metalbearin'g pulpj I invention" possesses "numerous other ob- 'jects and features of advantageysorne of which, together with the foregoing, will be set forth in the following description of specific apparatus embodying and utilizingmy novel method. It is '25 therefore to beunderstoodthat my method is applicable to other apparatus','and that I do not limit myself, in any ,w y, to the apparatus of the, present application, as I I may adopt various other I apparatus embodiments, utilizing 'the method, within the scope of the appended claims.

In the drawings:

Figure 1 is a diagrammatic, longitudinalzsectional view ofaseries of deckitr'ays employing "my invention. a

' T Figure 2 is a cross-sectionalview taken as i.n-.

dicated by line 2-2 in Figure 1. g 1 Figure 3v is a cross-sectionalview takenvas indicated by line 3-3 in Figure v 1 Figure 4 is a cross-sectional view taken, as indicated by line 44 in Figure 1 with the addition of a circuitdiagram, I

Figure 5 is a top viewof a portion of. a deck tray.

mental runs. These solutions of sodium "and run from oneinto the next.

of'the pulp on the surface of the mercury, a

mated surface.

Figure 6. is a view partly in cross-section: and

,is identical with the mercury trap M.

may also add the same solutions to the pulp until -a suitable consistency is obtained to secure maximum recovery of the precious metals containedj-in t-he-pulp, The ratiobetweensolutions. and solidsfor maximum recovery has to be established for each particular deposit by expert,

potassium'salts will hereafter bereferred to as the electrolyte. I g

The pulp is then fedinto a feed boxl, from whence it flows into deck trays 2, 3, a'ndd, placed 0mm anglejand overlapped so that the pulp will g The deck trays 3, and 4, are preferably made of copper and have an-amalgamated mercuryinner'surface. Metallicmercury --is, continually fed-to the top of the surface just before the pulp enters tray 2, *20 through a'mercury tube 5 from a mercury con-, tainer 6, and sufficient mercury is continually -fed so that there is, by gravity and by theaction continuous flow of mercury over the amalga- I Inorder to check the speed of the mercury flow and to add a rifiiing action to the amalgamator flow; I'may'Wish to place a cross *riflle 1 within one or more of the copper trays.

After the pulp has passed over thecopper trays- '2,'3, and 4,, it passes into a main mercury trap tray 8;".This traydiffers from the prior trays in that-it has a metal base plate 9, preferably,

iron, on Whicha copper plate. H3 is fitted, the

copper plate only being amalgamated, a'ndat the 35 lower end of the trap tray 8 there is a main mer cury-;trap ll extending across the tray. The amalgamated plate "Ill extends into the mercury trapill ,.'and at the side-of, the trap, shown in -Figure 2, there is, a mercury removal valve iii through which the mercury. may be allowed to k pass'continuously in accordancewith the rate of ,girrival in the trap. This mercury will contain thelgreater portion of the values reccvereisndf 'is'th'e'n treated for therenioval of these values.

The cleaned and condensed mercury may then "be returned to mercury container 6.

.Iffor anyreason all of the mercury is not caught in the main mercurytrap II, it may be collected in an auxiliary mercury trap M which A cross, section (if the auxiliary mercury trap is shop-'11 in Figure 3; and the mercury collected. therein may bev periodicallyremoved through mercury moval tube I 5. After the pulp has passed over:

blocks 25. I prefer tohave the fastening adjust able. v

A connection 26 is' made to the trays, and a connection 21 is made to the zinc plates. A

double throw switch 29 is provided so that the r external circuit between connections 26 and 21, and consequently the galvanic cell formed by the zinc plates and the trays maybe shorted in one position of the switch. At the other position of the switch an exterior source of potential 30 may be applied in series with the galvanic cell formed by the zinc plates and the trays.

I prefer, also, to set up the entire device in a sub-frame 3| mounted on hinged arms 32, the

latter being also hinged to a base 34. A prime mover drives a crank 36 which is attached by a connecting arm 31 to one of the arms 32, the end of the arm 31 being mounted in a slot 39 in that arm so that a variable throw may be obtained by moving the end of the arm 37 along the slot. The entire foundation ;34 is mounted on graduated blocks to obtain theproper inclination.

Having thus described the mechanical setup of my invention, I will now describe the method of operation. I H i As before stated, the pulp is fed into the hopper I and passes along the inclined trays over the mercury surfaces. The pulp and electrolyte as referred to above is fed to the traysin sufficient amounts so that the pulp forms a layer II, as shown in Figure 4, just below the zinc plate II, but I prefer to have enough electrolyte in prises the use of a galvanic cell in which the negative electrodes" are the zinc plates I1. In this respect I do not wish to be limited to the use of zinc, as any metal suitable because of its position in the electromotive force series may be "utilized. The positive electrode is the mercury surface of the amalgamated plates and the electrolyte is the dilute solution of the sodium or potassium salts that is added to the pulp. Since in the E. M. F. series zinc is .770 volt negative relative to hydrogen, and mercury is .748 volt positive to hydrogen, there will be a total E. M. F. of 1.518 volts between the two electrodes when no current is passing through the cell. If the circuit is completed through the external switch 29, a current flows from the zinc plate to the- 011 the mercury surface. I

removed by momentary use of the external mercury on the trays. This galvanic current dissociates the sodium and potassium salts, frees the alkali. metal from solution, and the alkali metal is then deposited on the surface of the mercury and immediately amalgamates therewith. The water, present in the electrolyte acts I on the freshly deposited alkali metal, producing a hydroxide. This reaction keeps the surface of the mercury clean and active,'as the-cell is shorted during recovery except for the intermittent use of external voltage hereafter described. r

When a particle of gold, for example, is brought into contact with the mercury by concentration from thepulp, the galvanic action at the point of contact of the mercury with the gold is in tensified due to the fact that a newgalvanio couple is formed, with the zinc acting as a negative and the gold acting as a positive electrade. Since gold is 1.079 volts positive relative to hydrogen, the galvanic action is" intensified and the subsequent electrolytic action accelerates the rate of amalgamation of the gold.

With regard to the particular type of electrolyte used in practice, I have found that by using sodium sulphate alone I have obtained good recovery of gold and fair recovery of silver. The

use of small percentages of potassium sulphate with the sodium sulphate has increased the recovery in such cases wherethe pulp contained minerals that discolored the bright mercurysur:

face; more difficult in that so ,much hydrogen is generated that the gold does not come in contact with the amalgamated surface, and I have found .that one good electrolyte ratio is five per cent Too much potassium salt renders recovery I have also foundthatjit is advisable to which may be utilized to short circuit the galvanic cell as above described or to additionally energize the cell, I prefer at all times to utilize the external current through the cell intermittently,

inasmuch as I have found that intermittent ac-' tion gives me a far higher recovery than can be possibly obtainedby constant action. Intermittent use, however, gives consistent and efficient removal, and often the period can be determined by watching themercury surfaces to determine the brilliance thereof. The current is used only when the mercury surface dulls. In practice;

short energization periods at intervals of fifteen minutes has been found sufilcient with some ores.

The external current source which .may be utilized by means of the double throw switch 29, is only used when it is necessary to clean the deck plates due to heavy contamination by certain minerals occurring in the deposit, or when it is desired to amalgamate platinum or certain silver compounds occurring in nature.

Even when the external source is utilized, how- I ever, the current is only used intermittently. .-1 For example, in the full or partial reduction'of certain sulphides, reddish brown spots are left With regard to platinum, it has"beenfound that platinum does not amalgamate readily un-. less an external M. F. is used, and not at all if the same is used continuously. By far the These spots are easily a 7c best results. are obtained by intermittent use, the period being different, depending upon the other minerals to be recovered and the character of the deposit. Ithas also been found that the amalgamation is not particularly rapid if only an external E. M. F is used, that is, when the amalgamator itself is not a galvanic cell.

From the tests which I have made comparing weighed samples of oretreated in various ways including the process described above, I am inclined to believe that 'a high recovery is obtained because the galvanic action increases the settling of the fine sliinesand cleans all surfaces and value particles. sulphides in the tailings were cleanand bright. Other tests have shown that gold which is dirty or greasy is rapidly and efficiently amalgamated,

probably due to the action of the caustic alkalies developed during the passage over the deck trays. Tests conducted with naturally coated gold showed that the humic acid of which the coating is'mostly made up, in some manner comb-ines with the alkali salts or with the metallic alkali metals deposited by the galvanic action,

and that the mercury spreads over the gold and amalgamates it, leaving nothingbut a few grains of silica and iron oxide on the surface of the mercury. I

I have, therefore, by the use of the process above described and the preferred'form of apparatus, been able to make high recoveries, .particularly of the finer values in pulp,- and my process has the advantage that it is continuous, with a continuous removal of the values without the'necessity of shutting down the flow, In that regard, the continuity of my preferred setup is shown in Figure 8, where the pulp, alkali salts, and mercury are fed to the amalgam plates and the amalgam is continuously removed, treated to recover the precious metals, and the mercury returned to the input end. In like manner the discharge from the almalgam plates may be run in a settling tank, the salts removed and passed back to the input end of thedevice, and the tailings further treated chemically if desired.

While I have described my preferred form of apparatus as utilizing copper amalgam plates, it is within the knowledge of those skilled in the art to use equivalent amalgam plates, as for example, silver plates, and it is also within the knowledge of those skilled in the-art to rearrange, extend, or change the tray setup within the scope of the appended claims.

I claim:

1. The method of recovering metal values from a wet pulp by amalgamation with mercury which comprises mixing an alkaline electrolyte with said pulp, passing the resultant pulp over a mercury surface, immersing a material electro-negative to the amalgamatedsurface in said pulp, and directly shorting said material to said surface. i

2. The method of recovering metal values from a wet pulp by amalgamation with mercury which comprises mixing an alkalimetal sulphate electrolyte with said pulp, passing the resultant pulp over a mercury surface, immersing a material electro-negative to the amalgamated surface in said pulp, and directly shorting said material to saidsurface.

3. The method of recovering metal values from a wet pulp by amalgamation with mercury which comprises mixing an alkali metal sulphate electrolyte with said pulp, passing the resultant pulp I .have also found that the l over a mercury surface, immersing a material,

electro-negative to the amalgamated surface in said pulp, and directly shorting said material to said surface.

i. The method of recovering metal values from a wet pulp by amalgamation with mercury which comprises mixing an alkali metal salt electrolyte with said pulp, passing the resultant pulp over a mercury surface, utilizing said mercury surface asthe positive pole of a galvanic cell in said electrolytic pulp, and shorting said cell. 5. The method of electrically cleaning amer- I cury, surface covered by a value bearing pulp which comprises adding an alkali metal salt so-- lution .to said pulp, passing the wet pulp over said surface, immersing a material electro-negative to the amalgamated surface in said pulp, directly shorting said material to said surface, and cleaning said surface byintermittently passing additional current through said pulp to said surface.

6. An amalgamator comprising an inclined tray,

a mercury amalgamated surface on the bottom of said tray, means for introducing a wet value bearing pulp including an electrolyte at the high end of said tray, means for simultaneously introducing metallic mercury at the high end of said tray, means for separating the pulp and mercury at the low. end of said tray, an electronegative electrode positioned over a substantial area of said mercury surface, insulated therefrom and end of said tray, means for separating the pulp and mercury at the low end of said tray, an electro-negative electrode positioned over a substantial area of said mercury surface, insulated therefrom .and immersed in said pulp, external'means for shorting said electrode to said surface, means for alternatively and intermittently placing an exterior source of potential in series with the galvanic cell formed by said electrode and said surface in said pulp.

8. The method of recovering metal values from a wet pulp by amalgamation, comprising adding to the pulp an electrolyte composed of approximately ninety-five per cent of sodium sulphate and approximately five per cent of potassium sulphate, passing said pulp between and in contact with a pair of interconnected electrodes occupying Y different positions in the 'electromotive series to create galvanic action through the reaction of said electrolyte and said electrodes, one of said electrodes containing mercury, and causing the formation of temporary localized galvanic couples by the deposition of particles of such values onthe surface of said mercury containing electrode. i Y i 9. The method of recovering metal values from a wet pulp by amalgamation, comprising adding an electrolyte to such pulp, passing said pulp between and in contact with a pair of electrodes, one of which includes'mercury, exposing such pulp to a continuous flow of current of a relatively low magnitude between said electrodes and intermittently increasing the magnitude of such current. f GEORGE MALMGREN. 

